1. Field of the Invention
The present invention relates to a collapsible steering column assembly for a motor vehicle.
2. Description of the Prior Art
Collapsible steering column assemblies are designed to absorb at least a portion of force exerted when an operator strikes a steering wheel during a collision event by allowing a collapsing movement of a steering column along a longitudinal axis. Steering column assemblies also commonly allow the operator to adjust a position of the steering wheel relative to the operator for driving comfort during normal vehicle operation. Common adjustments include telescoping movement of the steering column along the longitudinal axis and tilting or raking movement of the steering column along a pivot axis. Collapsible steering column assemblies generally include at least one of these adjustments.
Energy absorbing devices are commonly incorporated into collapsible steering column assembly designs. Generally, the energy absorbing device is an additional single function component such as a deformable metal strap or wire, added to the steering column assembly solely to absorb energy during the collision event. Occasionally the energy absorbing devices also serve another function. An example of such an assembly is disclosed in U.S. Pat. No. 5,961,146 to Matsumoto, et. al.
The steering column assembly of the Matsumoto '146 patent allows the collapsing and tilting movements of the steering column as previously discussed. A wire is used primarily as the energy absorbing device and can also be used as a biasing device to help support the steering column during the tilting movement. A support bracket is mounted to the vehicle and the jacket is mounted to a carriage bracket which is coupled to the support bracket by a locking mechanism. The locking mechanism includes a lock bolt. The biasing device is connected to the carriage bracket and moves with the jacket along the longitudinal axis during the collapsing movement. The support bracket and locking mechanism, including the lock bolt, remain connected to the vehicle during the collapsing movement. Energy from the jacket is transferred to the biasing device as the biasing device is pulled over and bent around the lock bolt, severely deforming the biasing device.
There remains a need for an energy absorbing device that adapts existing components of the steering column assemblies without degrading or compromising the effectiveness of the components. Additionally, there remains a need for an energy absorbing device which uses an existing component such as a biasing device in steering column assemblies that incorporate the telescoping movement.